1. Field of the Invention
The invention relates to a protecting device and to a method for shutting off a power supply, and is designed to protect terminals by preventing arcs from being created between the terminals electrically disconnected when a power supply circuit in a relay block connected with a battery in an automotive vehicle is broken for maintenance or the like.
2. Description of the Related Art
The power supply from a battery should be shut off before conducting maintenance on various types of electrical equipment in an automotive vehicle, such as maintenance on a navigation system or a radio.
Batteries installed in a conventional passenger vehicle typically have been rated 12V or at maximum 14V. However, the number of electrical devices installed in automotive vehicles has increased recently and the amount of current supplied to each electrical device also has increased in recent years. Accordingly, high-voltage batteries of 36V to 200V have been proposed.
Safety considerations mandate shutting off the power supply from a high-voltage battery before conducting maintenance of electrical equipment with a power supply from a high-voltage battery.
In view of the above, a protecting device has been developed. The protecting device has a fixed member with a power supply connected circuit and a load-connected circuit. A protection plug is mounted detachably in the fixed member and has a power supply switching circuit for connecting the power supply connected circuit and the load-connected circuit. The fixed member may be accommodated in a relay block connected with a battery.
The power supply connected circuit and the load-connected circuit of the above-described protecting device are connected electrically by connecting a terminal of the circuit in the protection plug and a terminal of a circuit in an electrical connection box. The protection plug is detached from the fixed member to disconnect the terminals from each other for maintenance.
However, the use of a high-voltage battery creates the likelihood for an arc between the terminals when the protection plug is detached from the fixed member to disconnect the terminals. The arc can damage the terminals.
The invention was developed in view of the above problem and an object thereof is to prevent the creation of an arc between terminals when a protection plug is detached from a fixed member at the time of maintenance.
The invention is directed to a protecting device in which a protection plug or member for switching a power supply circuit is mounted detachably to a fixed member to connect a movable circuit in the protection plug and a fixed circuit of the fixed member and to form a power supply circuit for supplying a power to a load. The power supply circuit is broken by detaching the protection plug. An input contact portion, a temporal circuit contact portion and an output circuit portion are provided between a terminal in the movable circuit of the protection plug and a terminal in the fixed circuit of the fixed member. The input contact portion and the output contact portion are closed or electrically turned on to supply power to the load and the temporal circuit contact portion is opened or electrically turned off in a normal state where the protection plug is mounted to the fixed member. The temporal circuit contact portion is closed or electrically turned on and connected with the power supply circuit with the input and output contact portions closed or electrically turned on at a first stage during the detachment of the protection plug. Either one of the input and output contact portions is opened or electrically turned off at a second stage. The temporal circuit contact portion is opened or electrically turned off at a third stage, and the other of the input and output contacts is opened or electrically turned off at a fourth stage.
The temporal circuit contact portion is off in the normal state where the protection plug is mounted to the fixed member of the above-described protecting device to prevent the creation of an arc when the power supply circuit is broken. The temporal circuit contact portion is temporarily turned on when the power supply circuit is broken by detaching or manipulating the protection plug. Thus, no arc is created between the terminals when the input and output contacts of the power supply circuit are separated.
Specifically, the temporal circuit contact is closed (or electrically turned on) with both input and output contacts closed, thereby connecting with a power supply side circuit and/or a load side circuit of the fixed circuit via the temporal circuit. The power supply and the load are connected via the temporal circuit when the input contact of the power supply side circuit or the output contact of the load side circuit connected with the temporal circuit is opened (turned off) at the second stage. This can prevent an arc from being created between the terminals to be disconnected.
The temporal circuit contact is opened or electrically turned off after the input contact or the output contact is turned off. At this time, there is a possibility of creating an arc between the fixed terminal for temporal circuit of the fixed member and the movable terminal for temporal circuit of the protection plug forming the temporal circuit contact portion since these two terminals are disconnected in an electrically conductive state. However, the temporal circuit contact preferably is made of an arc resistant material. Thus, the terminals at the temporal circuit contact portion are unlikely to be damaged even if an arc is created. Even if they should be damaged, it does not present a big problem as compared to a case where the terminals at the output and input contact portions are damaged as these terminals are not intended for power conduction in a normal state.
One of the input and output contact portions is opened or electrically turned off to separate the terminals after the temporal circuit contact portion is turned off. At this time, the temporal circuit contact portion is already off and the other of the input and output contact portions is already off and, hence, the fixed circuit and the movable circuit are electrically disconnected, i.e. no current flows between these two circuits. Therefore, there is no danger of creating an arc between the terminals being disconnected to damage the terminals.
The terminals at the input and output contact portions, which are closed (or electrically turned on) in the normal state to form the power supply circuit, are not damaged. Thus, the electrical connection reliability of the power supply circuit can be improved.
One and the other of a movable terminal for temporal circuit of the protection plug and a fixed terminal for temporal circuit of the fixed member forming the temporal circuit contact portion may have a first contact comprising a long protuberance that is long substantially along a detachment direction of the protection plug and a second contact comprising a small protuberance.
Preferably, the first and second contacts are separated or electrically turned off in the normal state where the protection plug is mounted to the fixed member and are brought into sliding contact with each other during the detachment of the protection plug to enable a control of on-off periods.
One and the other of a movable terminal for temporal circuit of the protection plug and a fixed terminal for temporal circuit of the fixed member forming the temporal circuit contact portion preferably have a first contact made of a vertically long protuberance and a second contact made of a small protuberance. The first and second contacts are separated or electrically turned off in the normal state where the protection plug is mounted in the fixed member and are brought into sliding contact with each other during the detachment of the protection plug, thereby enabling a control of on-off periods.
A fixed terminal for temporal circuit of the fixed member forming the temporal circuit contact portion may comprise a spring piece biased in a direction to contact a movable terminal for temporal circuit of the protection plug and a second contact projects from the spring piece.
A movable terminal for temporal circuit of the temporal circuit contact portion in the protection plug may comprise a tab projecting towards the fixed member from a casing of the protection plug. A first contact may project from the tab and an insulating guide piece may project from the casing at the side of the tab.
The first and second contacts preferably are spaced apart although the insulating guide piece biases the spring piece toward the movable terminal for temporal circuit in the normal state where the protection plug is mounted to the fixed member. The first contact of the movable terminal for temporal circuit preferably is moved into contact with the second contact and the fixed terminal for temporal circuit is returned substantially to its original shape by its spring force when the insulating guide piece is disengaged therefrom to separate the first and second contacts at the first stage during the detachment of the protection plug.
A fixed terminal for temporal circuit of the fixed member forming the temporal circuit contact portion preferably is formed of a spring piece biased for contact with a movable terminal for temporal circuit of the protection plug and a second contact projects from the spring piece. However, a movable terminal for temporal circuit of the temporal circuit contact portion in the protection plug is formed of a tab that projects down from a casing of the protection plug, a first contact projects from the tab and an insulating guide piece projects from the casing at the side of the tab. The first and second contacts are spaced apart, but the insulating guide piece biases the spring piece toward the movable terminal for temporal circuit in the normal state where the protection plug is inserted in the fixed member, the first contact of the movable terminal for temporal circuit is moved for contacting the second contact and the fixed terminal for temporal circuit is returned to its original shape by its spring force when the insulating guide piece is disengaged to separate the first and second contacts at the first stage during the detachment of the protection plug.
The on-off periods of the temporal circuit contact portion may be controlled by adjusting the length of the slidable first contact or by the combination of the spring piece and the insulating guide piece.
Specifically, the fixed terminal for temporal circuit of the temporal circuit contact portion is formed of a spring piece biased in a direction to open the contact portion and the second contact in the form of a small protuberance projects from the spring piece. However, the movable terminal for temporal circuit of the protection plug is formed of a tab projecting down from the casing of the protection plug, and the vertically long first contact projects from the tab and the insulating guide piece projects out of the casing at the side of the tab.
In the normal state where the protection plug is inserted, the insulating guide piece biases the fixed terminal for temporal circuit in a direction to bring it into contact with the movable terminal for temporal circuit of the protection plug against the spring force, but the second contact is spaced up from the first contact. Thus, the temporal circuit contact portion is open.
The movable terminal for temporal circuit is moved up to bring the first contact into contact with the second contact to thereby close the temporal circuit contact portion at the first stage during the detachment of the protection plug, and the insulating guide piece is disengaged from the fixed terminal for temporal circuit at the third stage, thereby returning this terminal to its original position to open the temporal circuit contact portion.
There is a possibility of creating an arc when the terminals at the temporal circuit contact portion are disconnected, these terminals are made of a more arc resistant material than of the input and output contact portions, such as a Agxe2x80x94Cdo material, a Agxe2x80x94Ni material, a Ag-metallic oxide material and an Ag-Gr material, so as not to be damaged even if an arc is created.
Preferably, the movable terminal for temporal circuit and/or the fixed terminal for temporal circuit are made of an arc resistant material.
Tabs that will form the input and output contact portions preferably project toward the protection plug or up in the fixed circuit of the fixed member. The tab of the input contact portion projects a longer distance than that of the output contact portion. Recesses are formed in the mating side surfaces or bottom end surfaces of projecting portions or downward-projecting portions at the opposite sides of a casing of the protection plug, and female terminals connectable with the corresponding tabs are mounted in these recesses. The tabs and the female terminals at the input and output contact portions preferably are still connected with each other at the first stage during the detachment of the protection plug. The female terminal of the output contact portion is separated from the corresponding tab at the second stage, and the female terminal of the input contact portion is separated from the corresponding tab to open the input contact portion at the fourth stage after the temporal circuit contact portion is opened or electrically turned off.
The downward-projecting portions are provided at the opposite sides of the casing of the protection plug, the bottom end surfaces of the downward-projecting portions are located at the same height, and the recesses are formed in these bottom end surfaces. The depths of the recesses are preferably made larger at the input terminal side than at the output terminal side, the output contact portion and the input contact portion are closed (or electrically turned on) in the normal state where the protection plug is mounted in the fixed member, and the output contact portion is turned off earlier than the input contact portion when the protection plug is pulled upward.
An electrically conductive plate having the opposite ends connected with the input terminal and the output terminal is built in the casing of the protection plug, and the terminal (movable terminal for temporal circuit) of the temporal circuit contact portion formed by a tab branched off from the electrically conductive plate projects downward from the inside of the casing.
The insulating guide piece is so caused to project downward as to face this tab, and the temporal circuit contact portion is opened (or electrically turned off) by the disengagement of the insulating guide piece from the spring piece before the input contact portion is opened (or electrically turned off).
A ground circuit preferably is branched off from the temporal circuit contact portion between the terminal of the temporal circuit contact portion and the output contact portion in the fixed circuit of the fixed member.
A ground circuit is branched off between the terminal of the temporal circuit contact portion and the tab of the output contact portion in the fixed circuit of the fixed member. The ground circuit is provided with a ground circuit contact portion where a spring piece is brought resiliently into contact with a tab, and an insulating bar projects from the protection plug. The insulating bar is inserted between the spring piece and the tab to open the ground circuit contact portion in the normal state where the protection plug is inserted in the fixed member, and the insulating bar is disengaged from the ground circuit contact portion to close the ground circuit contact portion and connect the load with the ground circuit after the input contact portion is opened (or electrically turned off) at the fourth stage during the detachment of the protection plug.
The ground circuit preferably is branched off between the terminal of the temporal circuit contact portion and the tab of the output contact portion in the fixed circuit of the fixed member.
The ground circuit preferably is provided with a ground circuit contact portion where a spring piece is brought resiliently into contact with a tab.
An insulating bar preferably projects from the protection plug, and the insulating bar can open the ground circuit contact portion in the normal state where the protection plug is mounted to the fixed member by being insertable between the spring piece and the tab. The insulating bar can close the ground circuit contact portion and allow a connection of the load with the ground circuit by being disengageable from the ground circuit contact portion, after the input contact portion is opened at the fourth stage during the detachment of the protection plug.
The insulating bar of the protection plug for opening and closing the ground circuit contact portion is formed integrally or unitarily at the middle recess of the casing of the protection plug and projects down toward the fixed member. The insulating bar projects farther than the downward projecting portions at the opposite ends, so that the insulating bar is disengaged from the terminals at the final stage where the input contact portion is opened (or electrically turned off), thereby closing the ground circuit contact portion. In this way, the load-side circuit shut off from the battery is connected with the ground circuit to ground the electrical charges residual in the load-side circuit.
Preferably, the fixed member is mounted in an accommodating portion formed in a relay block, and an upstream end of the fixed circuit of the fixed member is connected with a high-voltage battery of 36V to 200V.
As described above, when the high-voltage battery is used, the safety of the maintenance can be improved if the protection plug is provided in the relay block at a position near the battery to shut off the power supply at the time of maintenance. Further, since an arc is likely to be created between the terminals being disconnected at the time of shutting off the power supply if the high-voltage battery is used, the damage of the terminals due to the arc created between the terminals being disconnected at the input contact portion can be prevented if the temporal circuit contact portion is provided in the protection plug and the power supply is shut off by stepwise opening the contact portions from the output contact portion to the temporal circuit contact portion and to the input contact portion.
The invention relates to a method of shutting off a power supply by means of a protecting device in which a protection plug for switching a power supply circuit is detachably mountable to a fixed member to connect a movable circuit in the protection plug and a fixed circuit of the fixed member and form a power supply circuit for supplying power from the power supply to a load. The power supply circuit is broken by detaching the protection plug. The method comprises providing an input contact portion, a temporal circuit contact portion and an output circuit portion between a terminal in the movable circuit of the protection plug and a terminal in the fixed circuit of the fixed member. The method then comprises closing or electrically turning on the input contact portion and the output contact portion to supply power to the load and opening (electrically turning off) the temporal circuit contact portion in a normal state where the protection plug is mounted to the fixed member. The method further comprises closing or electrically turning on the temporal circuit contact portion and connecting it with the power supply circuit with the input and output contact portions closed at a first stage during the detachment of the protection plug. The method continues by opening (electrically turning off) either one of the input and output contact portions at a second stage. The method then includes opening (electrically turning off) the temporal circuit contact portion at a third stage, and opening (electrically turning off) the other of the input and output contact portions at a fourth stage.
Control of on-off periods may be performed by geometrically shaping the terminals for temporal circuit of the protection plug and for temporal circuit of the fixed member differently.
Preferably, one and the other of a movable terminal for temporal circuit of the protection plug and a fixed terminal for temporal circuit of the fixed member forming the temporal circuit contact portion are provided with a first contact comprising a long protuberance being long substantially along a detachment direction of the protection plug and a second contact comprising a small protuberance.
The temporal circuit contact portion may be opened and/or closed by a fixed terminal for temporal circuit of the fixed member forming the temporal circuit contact portion and comprising a spring piece biased in a direction to be brought into contact with a movable terminal for temporal circuit of the protection plug. A second contact projects from the spring piece.
A movable terminal for temporal circuit of the temporal circuit contact portion in the protection plug may comprise a tab projecting towards the fixed member from a casing of the protection plug. A first contact projects from the tab and an insulating guide piece projects from the casing at the side of the tab.
The first and second contacts preferably are spaced apart although the insulating guide piece biases the spring piece toward the movable terminal for temporal circuit in the normal state where the protection plug is mounted to the fixed member. The first contact of the movable terminal for temporal circuit is moved for contact with the second contact and the fixed terminal for temporal circuit is returned substantially to its original shape by its spring force when the insulating guide piece is disengaged therefrom to separate the first and second contacts at the first stage during the detachment of the protection plug.
According to a further preferred embodiment, the movable terminal for temporal circuit and/or the fixed terminal for temporal circuit are made of an arc resistant material.
Tabs which will form the input and output contact portions preferably project toward the protection plug in the fixed circuit of the fixed member, the tab of the input contact portion projects farther than that of the output contact portion, recesses are formed in the mating end surfaces of projecting portions at the opposite sides of a casing of the protection plug, and female terminals connectable with the corresponding tabs are mounted in the recesses.
Preferably, the tabs and the female terminals at the input and output contact portions are still connected with each other at the first stage during the detachment of the protection plug. The female terminal of the output contact portion is separated from the corresponding tab at the second stage. The female terminal of the input contact portion is separated from the corresponding tab to open the input contact portion at the fourth stage after the temporal circuit contact portion is opened.
The method further may comprise the step of branching off a ground circuit from the temporal circuit contact portion between the terminal of the temporal circuit contact portion and the output contact portion in the fixed circuit of the fixed member.
The ground circuit may be branched off between the terminal of the temporal circuit contact portion and the tab of the output contact portion in the fixed circuit of the fixed member.
The ground circuit preferably has a ground circuit contact portion where a spring piece is resiliently brought into contact with a tab.
The ground circuit contact portion preferably is opened by an insulating bar projects from the protection plug in the normal state where the protection plug is inserted in or mounted to the fixed member by being insertable between the spring piece and the tab. The ground circuit contact portion is closed by the insulating bar thus allowing a connection of the load with the ground circuit by being disengageable from the ground circuit contact portion, after the input contact portion is opened at the fourth stage during the detachment of the protection plug.
Most preferably, the fixed member is fixed in an accommodating portion formed in a relay block, and an upstream end of the fixed circuit of the fixed member is connected with a high-voltage battery of 36V to 200V.
These and other objects, features and advantages of the present invention will become more apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings. It should be understood that even though embodiments are separately described, single features thereof may be combined to additional embodiments.